DS18B20-PAR 1-Wire Parasite-Power Digital Thermometer

DS18B20-PARthe read time slot. Therefore, the master must release the bus and then sample the bus state within 15 sfrom the start of the slot.Figure 14 illustrates that the sum of T INIT , T RC , and T SAMPLE must be less than 15 s for a read time slot.Figure 15 shows that system timing margin is maximized by keeping T INIT and T RC as short as possibleand by locating the master sample time during read time slots towards the end of the 15 s period.DETAILED MASTER READ 1 TIMING Figure 14V PU1-WIRE BUSVIH of MasterGNDT INT > 1 sT RCMaster samples15 sRECOMMENDED MASTER READ 1 TIMING Figure 15V PU1-WIRE BUSVIH of MasterGNDT INT =smallT RC =small15 sMaster samplesLINE TYPE LEGENDBus master pulling lowResistor pullupDS18B20-PAR OPERATION EXAMPLE 1In this example there are multiple DS18B20-PARs on the bus. The bus master initiates a temperatureconversion in a specific DS18B20-PAR and then reads its scratchpad and recalculates the CRC to verifythe data.MASTER MODE DATA (LSB FIRST) COMMENTSTX Reset Master issues reset pulse.RX Presence DS18B20-PARs respond with presence pulse.TX 55h Master issues Match ROM command.TX 64-bit ROM code Master sends DS18B20-PAR ROM code.TX 44h Master issues Convert T command.TXDQ line held high bystrong pullupMaster applies strong pullup to DQ for the duration of theconversion (t conv ).TX Reset Master issues reset pulse.RX Presence DS18B20-PARs respond with presence pulse.TX 55h Master issues Match ROM command.TX 64-bit ROM code Master sends DS18B20-PAR ROM code.TX BEh Master issues Read Scratchpad command.15 of 19